I learned something that explains why my daughter can have a lower-GI-only IgE allergy to soy and other legumes. She literally only gets tummy ache and diarrhea. This article suggests only her mast cells in her lower GI tract have been primed with IgE targeting these legumes.
Before an allergic reaction can occur, a person who is predisposed to form IgE to foods first has to be exposed to the food. As this food is digested, it triggers certain cells to produce specific IgE in large amounts. The IgE is then released and attaches to the surface of mast cells. The next time the person eats that food, it interacts with specific IgE on the surface of the mast cells and triggers the cells to release chemicals such as histamine. Depending upon the tissue in which they are released, these chemicals will cause a person to have various food allergy symptoms. If the mast cells release chemicals in the ears, nose, and throat, a person may feel an itching in the mouth and may have trouble breathing or swallowing. If the affected mast cells are in the gastrointestinal tract, the person may have abdominal pain, vomoting, or diarrhea. The chemicals released by skin mast cells, in contrast, can prompt hives.
http://www.webmd.com/allergies/guide/fo ... tolerances
